Hybrid forming method and corresponding forming device

ABSTRACT

A hybrid method for forming a material blank includes placing a material blank to be deformed between a die and a blank-holder. The material blank is deformed by stamping using at least one punch in order to obtain a pre-stamped material blank. A cavity, wherein, on one hand, the at least one punch having pre-stamped the material blank and, on the other, at least one pair of electrodes are located, is filled with liquid. The pre-stamped material blank is placed in contact with the liquid of the cavity, and at least one electrical discharge is generated between the at least one pair of electrodes in such a way as to deform the pre-stamped material blank against the die.

BACKGROUND Technical Field

The present disclosure relates to a hybrid method for forming a sheetand a corresponding forming device.

Description of the Related Art

There are numerous methods for forming a sheet to give it a more or lesscomplex shape. The sheet can for example be bent, rolled, stamped, etc.

By way of method for deforming a sheet, electrohydraulic forming isknown which deforms a sheet against a mould by applying a dynamicpressure. For this purpose, an electrical discharge is generated betweenat least two electrodes in a cavity filled with liquid, for examplewater. An electric arc is then formed between the two electrodesinducing a high temperature gradient and vaporisation of the liquid. Apressure wave, also commonly known as a “shock wave”, moves at highspeed and presses the sheet against the mould. Electrohydraulic formingis particularly advantageous compared with other forming methods sinceit makes it possible to have a reduced elastic return and obtainenhanced etching type details and/or square edges and/or elongationsbefore break on the parts to be formed.

In some cases, particularly when the parts to be formed are particularlydeep, several successive electrical discharges can be carried out. Inorder to reduce the number of successive electrical discharges requiredand thus limit the forming time of a part, it has been proposed to carryout a hydraulic preforming step before the electrohydraulic forming ofthe part. To do this, the cavity is filled with pressurised liquid asdescribed for example in the document U.S. Pat. No. 7,802,457 B2. Whenthe liquid pressure is sufficient, the sheet is partially deformedagainst the mould. Electrical discharges are then generated to induceshock waves and complete the forming of the part until the desired shapeis achieved.

Preforming the part by applying a quasi-static pressure makes itpossible to promote the descent of the sheet in the mould, therefore toreduce the deformation of the material to be carried out byelectrohydraulic forming and therefore reduce the forming time should itbe necessary to recharge the high-voltage electrical pulse generatorbetween two discharges or reduce the size of the generator should it besought to carry out successive discharges without having to wait betweenthe discharges for the generator to recharge.

With these methods, it is however difficult to produce parts withvertical walls, i.e. walls extending perpendicularly to the plane of thesheet before the deformation thereof. To be able to produce suchvertical walls, very high pressures should be used.

The document US2011/0088442 relates to a hydromechanical forming toolthat may include electrohydraulic forming chambers in which anelectrical discharge can be induced by electrodes in order to improvethe level of the detail which can be produced in a mould.

The document DE 10019594 relates to a method and a device for thehydromechanical deformation of plastically deformable sheets, inparticular for producing motor body parts, wherein the sheet is placedbetween a forming tool and a liquid buffer and wherein under the effectof a static pressure created in the liquid buffer, the sheet is pressedagainst the forming tool. Simultaneously to the application of thestatic pressure, a shock wave generator disposed in the liquid buffer isactivated to locally create an increased pressure force oriented towardszones of the sheet.

The document US2012/103045 shows for its part a system for theelectrohydraulic forming of a sheet in an electro-hydroforming machine.

BRIEF SUMMARY

The present disclosure provides a method and a corresponding devicewhich makes it possible to produce simply, using electro-hydroforming,vertical walls.

To this end, the present disclosure proposes a hybrid method for forminga material blank wherein:

-   -   the material blank to be deformed is placed between a die and a        blank-holder,    -   the material blank is deformed by stamping using at least one        punch in order to obtain a pre-stamped material blank.

According to the present disclosure, the following steps are alsoprovided:

-   -   a cavity, wherein, on one hand, said at least one punch and, on        the other, at least one pair of electrodes are located, is        filled with liquid,    -   the pre-stamped material blank is placed in contact with the        liquid of the cavity, and    -   at least one electrical discharge is generated between at least        one pair of electrodes in such a way as to deform the material        blank against the die.

This method makes it possible to favour the descent of the material intothe die while offering the possibility of creating so-called verticalwalls using the punch and also having a high-quality finish of the partthanks to the electro-hydroforming.

According to a first alternative embodiment, the relative travel of eachpunch with respect to the die is limited in such a way that the materialblank when pushed by the punch(es) does not come into contact with thedie.

According to a further alternative embodiment, the relative travel of atleast one punch with respect to the die is such that the material blankwhen pushed by said at least one punch comes into contact with the die.

To further enhance the finish quality of the part produced andfacilitate the adjustment of the tools by limiting the manual reworkingof the punch, the hybrid method described above can further include astep during which the liquid in contact with the material blank ispressurised so as to deform the pre-stamped material blank. Ahydroforming step is then carried out which is preferably carried outafter the deformation by the punch and before the electro-hydroforming.

So as not to be impeded by the air remaining lodged between the materialblank and the die, it can be advantageously arranged to create anegative pressure between the material blank and the die.

In order to concentrate the shock waves created by the electricaldischarges, it has been observed that it is preferable to have arelatively great proximity of the punch with the material blank duringthe electro-hydroforming. Thus, it is arranged preferably to only movethe at least one punch away from the die after having carried out atleast one electrical discharge.

The present disclosure also proposes a device for implementing thehybrid formation method described above. It thus proposes a hybridmaterial blank forming device comprising:

-   -   a die cooperating with a blank-holder, the die being movable        relative to the blank-holder between a so-called open position        wherein the material blank can be positioned between the die and        the blank-holder and be removed therefrom, and another so-called        closed position wherein the blank-holder cooperates with the die        to hold in a controlled manner the entire edge of a material        blank to be deformed,    -   a tank defining a cavity capable of being filled with a liquid,    -   at least two electrodes placed in the cavity,

wherein

-   -   the tank includes at least one movable punch relative to an        assembly formed by the blank-holder and the die in the closed        position between a so-called far position wherein the free end        of the punch is at a distance from the die and a so-called near        position wherein the free end of the punch is at a distance from        the die less than the distancing distance in the far position.

In this structure, the die makes it possible to define the final shapeof the sheet to be deformed. The punch is arranged to be disposed in thecavity and to deform the sheet in the direction of the die by cominginto contact with said sheet and by deforming it.

In a preferred alternative embodiment of such a hybrid forming device,the assembly formed by the blank-holder and the die in the closedposition is movable with respect to the tank which remains stationary.

In this hybrid forming device, it can also be arranged that the tank hasa bottom and a peripheral wall, and that the free edge of the peripheralwall forms a punch. Here the tank and the at least one punch arepreferably a single part.

In the cases where the tank has a bottom and a peripheral wall, then itcan be arranged that at least one punch is produced on a free edge of awall extending through the tank by dividing the latter into at least twocompartments, and that at least one pair of electrodes is located ineach of the two compartments.

A preferred alternative embodiment of a device described above providesthat the blank-holder is attached to vertical stays, that the die ismovably mounted in translation with respect to the blank-holder on theside opposite the stays, that the tank includes a bottom and aperipheral wall, and that the tank is fixedly mounted whereas the staysare sliding with respect to the tank. These stays can be mounted forexample on hydraulic buffers. These stays can also be formed for exampleby a gas spring, a hydraulic cylinder or similar.

BRIEF DESCRIPTION OF THE DRAWINGS

Details and advantages of the present disclosure will emerge moreclearly from the following description, with reference to the appendedschematic drawing wherein:

FIG. 1 shows a first step of a hybrid method for forming a sheet, themethod being implemented with a hybrid forming device;

FIG. 2 shows a second step of a hybrid method for forming a sheet, themethod being implemented with a hybrid forming device;

FIG. 3 shows a third step of a hybrid method for forming a sheet, themethod being implemented with a hybrid forming device;

FIG. 4 shows a fourth step of a hybrid method for forming a sheet, themethod being implemented with a hybrid forming device; and

FIG. 5 shows a fifth step of a hybrid method for forming a sheet, themethod being implemented with a hybrid forming device.

DETAILED DESCRIPTION

The drawing and the description hereinafter contain, essentially,elements of a certain nature. They can therefore not only serve tobetter explain the present disclosure, but also contribute to thedefinition thereof, where applicable.

FIG. 1 represents a device for forming a material blank in alongitudinal cross-section through a vertical plane. It is assumedhereinafter in the description that the material blank to be deformed isa sheet 2, made of steel or of steel-based alloy, or indeed of anothermetal or metal alloy. Initially (FIG. 1), this sheet 2 is of a givenshape, for example planar as illustrated in FIG. 1. A cap-shaped sheetfor example could also be envisaged.

The sheet 2 to be deformed is placed here between a blank-holder 4 and adie 6. The blank-holder 4 is borne by stays 8 guided in housings formedin a bottom frame placed on the ground assumed to be horizontal andwhereon a tank 10 is securely attached.

It is assumed hereinafter in the description that the stays 8 extendvertically and that they support the blank-holder 4 which is thereforelocated above the stays 8. In this way, a top-down orientation isdefined. It will be retained throughout the remainder of the presentdescription.

The blank-holder 4 is disposed here below the sheet 2. It consists of anannular part having a top edge 14 adapted to the die 6 and to the shapeto be adopted by the sheet 2 after a first deformation (optionalpreforming operation described hereinafter).

Around the top edge 14, the blank-holder 4 has a peripheral rim 16serving as a support for compensating devices 18 intended to cooperatewith the die 6 in order to control the clamping forces exerted by thedie 6 and the blank-holder 4 on the sheet 2.

In the preferred embodiment illustrated in the drawing, the blank-holder4 has a cylindrical surface 20, having a cross-section adapted to theshape of the tank 10, of vertical axis. As explained hereinafter, thiscylindrical surface 20 makes it possible to create a seal between theblank-holder 4 and the tank 10.

The blank-holder 4 further has a bottom base 22 which rests on the stays8. The latter are used to support the blank-holder 4. They could alsohelp guide the blank-holder 4 with respect to the tank 10. These stayscan be for example gas springs or hydraulic cylinders. They may consistof rods mounted on hydraulic buffers. To guide the assembly formed bythe blank-holder 4, the die 6 and the sheet 2 clamped between these twoelements in translation with respect to the tank 10, external guidingmeans, not shown for drawing simplification purposes, are preferablyprovided.

The die 6 is the main part of the device which determines the finalshape of the sheet 2 after deformation. The bottom face of the die 6,i.e. that facing the blank-holder 4, is intended to give the final shapeof the sheet 2 after deformation. In the forming method, the sheet 2will be pushed against the die 6, more specifically against the bottomface of the die 6, to be plastically deformed and mould the shapethereof.

The bottom face of the die 6, which corresponds to the face of the die 6located facing, on one hand, the blank-holder 4 and, on the other, thetank 10, also includes an annular zone disposed opposite the top edge 14of the blank-holder 4. The edge of the sheet 2 will be held during theforming method between the top edge of the blank-holder 4 and theabovementioned annular zone of the bottom face of the die 6.

In the illustrated embodiment wherein it was considered that the tank 10was stationary, the die 6 is movable in a vertical translation movementso as to be able to move towards and away from the blank-holder 4 whichinitially is intended to remain stationary. The blank-holder 4 remainingstationary, the die 6 moves between the first position, or openposition, wherein the free space between the blank-holder 4 and the die6 is sufficient to insert a sheet 2 before deformation and remove itafter deformation, and a second position, or closed position, wherein itgrips the peripheral edge of the sheet 2 to be deformed between theannular zone thereof and the top edge 14 of the blank-holder 4. Thecompensating devices 18 provide a constant gap between the die 6 and theblank-holder 4 corresponding to the thickness of the sheet 2, plus orminus an adjustment value.

For simplification purposes, the drawing does not show the means usedfor moving the die 6. Such means are known to a person skilled in theart of conventional stamping for example.

The tank 10 fulfils here, in this preferred embodiment, the dualfunction of receptacle for containing liquid (preferably water) and ofpunch. It is hereinafter referred to as “tank” but could also bereferred to as “punch”. Alternatively, these two functions could beseparated, a separate punch being for example associated with a tank.This tank 10 has in the illustrated embodiment a base plate 24 fromwhich a peripheral wall 26 extends. The base plate 24 forms the bottomof the tank 10.

The peripheral wall 26 extends vertically and defines with the baseplate 24 (which extends substantially horizontally) a cavity capable ofbeing filled with liquid (generally water). The outer surface of theperipheral wall 26 cooperates with the cylindrical surface 20 of theblank-holder to provide tightness, for example using a seal 28, during avertical translation movement of the blank-holder 4 around theperipheral wall 26. Specific means, for example guiding columns notshown, preferably provide the guidance during a translation movement ofthe blank-holder 4 with respect to the tank 10. It is noted that thecylindrical surface 20 can form the top edge of the cavity defined bythe tank 10 and thus extend this cavity according to the relativeposition of the blank-holder 4 with respect to the tank 10.

In the illustrated embodiment, the top part of the tank 10 as mentionedabove forms at least partially the top face of the punch. Firstly, thefree edge (opposite the base plate 24) of the peripheral wall 26 has acontour of shape adapted to the deformation sought to be applied to thesheet 2. This free edge can thus include protruding and/or hollowedparts. Then, a wall 30, substantially vertical, is disposed in the tank10, inside the peripheral wall 26. This wall 30 starts from the baseplate 24 and extends vertically towards the die 6. The free end of thewall 30 forms a head 32 which is machined according to the shape to begiven to the sheet 2.

The wall 30 preferably divides the internal cavity of the tank intocompartments 34. The compartments can be tight with respect to eachother but communications (passages) can be provided therebetween.

Obviously, according to the final shape to be given to the sheet 2,several walls 30 can be provided in the tank. They can be parallel withrespect to each other, intersect perpendicularly or according to anyangle, and more generally be of any shape: straight, curved, undulated,etc.

In each compartment 34, or at the very least in at least some thereof, apair of electrodes 36 are disposed which are powered for example throughthe base plate 24 (connections and insulators not shown).

The presence of DH stops 38 is observed in the drawing, i.e. Die Heightstops, which, in a manner known to a person skilled in the art,precisely limit the end of travel of the die 6 (and also of the assemblyformed by the blank-holder and the sheet 2 actuated by the die 6 duringthe movement thereof). The DH stops are disposed on a stationary surfacesuch as for example here a top face of the bottom frame bearing the tank10, around the peripheral wall 26 and are disposed between this baseplate 24 and the bottom face of the die 6. They could also cooperatewith the bottom base 22 of the blank-holder 4.

FIG. 1 shows the hybrid forming device in a position corresponding to afirst step of a forming method. In this position, the die 6 is in theopen position, i.e. in the farthest position thereof from theblank-holder 4 (and from the tank 10 including the punch 26, 32). Asmentioned above, the blank-holder 4 and the die 6 are then quite spacedfrom each other to enable particularly the insertion of a sheet 2therebetween. FIG. 1 illustrates the positioning of this sheet 2, thispositioning being suggested by the arrow 40 on the left of this FIG. 1.

In the position in FIG. 1, the blank-holder 4 is in a high position,i.e. a position wherein the blank-holder 4 bearing the sheet 2 ispositioned in such a way that the top part of the tank 10 forming thepunch cannot come into contact with the sheet 2. Water can already bepresent in the compartments 34 of the tank 10. The die 6 is disposedabove the sheet 2.

FIG. 2 illustrates a subsequent step. With respect to FIG. 1, the die 6is lowered as suggested by an arrow 42. The peripheral edge of the sheet2 is gripped between the annular zone of the die 6 and the top edge ofthe blank-holder 4. The clamping force between the die 6 and theblank-holder 4 is set by compensating devices 18 which are disposedbetween the peripheral rim 16 of the blank-holder 4 and an edge of thedie 6 (also accounting for force compensation which can be carried outat the level of each of the stays 8). In the method illustrated in thedrawing, deformation of the sheet 2 is not provided during this step.The contact zones, on one hand, between the sheet 2 and the die 6 and,on the other, between the sheet 2 and the blank-holder 4 are preferablyparallel.

Alternatively, the clamping of the die 6 on the sheet 2 could be used inorder to carry out a first preforming of the sheet 2, for example tocurve the latter and/or to mould the edge thereof. It is thus possibleto induce (optionally) a first deformation on the sheet 2. The clampingof the die 6 on the blank-holder 4 furthermore makes it possible toensure water-tightness between the sheet 2 and the blank-holder 4. Aperipheral rod can also optionally be formed on the sheet 2 between thedie 6 and the blank-holder 4 to ensure satisfactory tightness betweenthe sheet 2 and the blank-holder 4. An elastomer seal can also fulfilthis tightness function.

Water then fills the entire space delimited by the inside of the tank10, the sheet 2, the cylindrical surface 20 of the blank-holder 4 andthe seal(s) 28. The aim of filling with water is to fill the cavity insuch a way that the liquid comes into contact with the optionallypreformed sheet 2. It can be carried out for example by sucking in theair located below the sheet 2. Simultaneous suction of the air above thesheet 2 is also carried out to maintain substantially the same pressureon both sides of the sheet 2. The suction of air between the sheet 2 andthe die 6 is preferably maintained throughout the deformation method toprevent the air located in this space from impeding the deformation ofthe sheet 2. Alternatively, it can be arranged to discharge the air viadischarge holes at a high point of the blank-holder 4 when water risesin the cavity. During this phase, if the sheet has a concave shape,pressurised air can be used to keep the sheet concave, thus limiting theair bubbles below it. The blank-holder 4 remains during this filling inthe same position as in FIG. 1.

Subsequently (FIG. 3), the die 6 continues to descend towards the tank10, and induces the descent of the blank-holder 4 with respect to thetank 10-arrow 44. The punch formed by the tank 10, more particularly thetop peripheral edge of the peripheral wall 26 and the head(s) 32 thencome into contact with the sheet 2 and deform it plastically bystretching. During this movement, the punch exerts a force pushing thesheet 2 towards the die 6. The sheet 2 held between the blank-holder 4and the die 6 is disposed between the punch and the die 6. The punchand/or the tank 10 act as a male part cooperating with the die 6, afemale part which here has a housing to receive the punch formed by thetop part of the tank 10. The compensating devices 18 act here toregulate the tension at the edge of the sheet 2 and allow if required amovement of material from the sheet 2 towards the inside of the system.

A second deformation step (the optional preforming mentioned above beingthe first deformation step) of the sheet 2 is carried out here. Itconsists here of a stamping step. During this deformation step, it issought preferably, but not obligatorily, to ensure that the sheet 2 doesnot touch the die 6 in the central zone thereof, i.e. in the zonelocated facing the inside of the peripheral wall 26. However, in somecases, a “full” deformation of the sheet 2 can be provided at certainlocations during this stamping operation. This makes it possible toavoid having to provide electrodes to “cover” the entire surface of thesheet 2.

FIG. 4 illustrates an advantageous but optional step of the hybridforming method. It is proposed here to have a step of quasi-statichydroforming of the sheet 2 during which this sheet 2 once againapproaches the die 6 and can locally come into contact therewith. Thisdeformation of the sheet 2 is then obtained by pressurising the waterlocated in the tank 10, for example by acting upon the die 6 (arrow 42).The sheet 2 is therefore separated at least locally from the punchformed by the top part of the tank 10 and adopts an intermediateposition between the die 6 and the head(s) 32 and the top edge of theperipheral wall 26 forming the punch.

A person skilled in the art will already have observed that the appendedfigures are schematic and merely illustrative. The deformations and thedetails are not to scale.

FIG. 5 illustrates a subsequent step of the method for forming the sheet2. An electro-hydroforming is shown schematically here. A dischargechamber is formed here and entirely filled with water. It comprises thecavity inside the tank and extends beyond up to the deformed sheet 2 andup to the seal created between the tank and the blank-holder 4. Thepairs of electrodes 36, disposed in said discharge chamber, are thenpowered by a strong current from a capacitor discharge. In a knownmanner, this electrical discharge creates in the liquid (water)contained in the tank 10 and in contact with the sheet 2 (it isimportant to have a satisfactory filling of water in the tank 10 suchthat the water is indeed in contact with the sheet 2 for thiselectro-hydroforming step) an explosion creating a shock wave which ispropagated towards the sheet 2. The wall(s) 30 and the peripheral wall26 guide the shock waves and thus act to enable a satisfactorydeformation of the sheet 2 against the die 6.

In this method, a single electrical discharge in the pairs of electrodes36 is normally sufficient to obtain the sought deformation thanks to theprior deformations of the sheet 2, before the electro-hydroforming step.

The drawing does not represent the final steps which relate to theremoval of the part which was formed from the sheet 2, with opening ofthe mould and relowering of the tank to the position thereof illustratedin FIG. 1.

The method described here therefore makes it possible to produce partswith a reduced cycle time as a single electro-hydroforming step isrequired. The stretch drawing and optionally hydroforming operations arecarried out virtually in masked time.

A great advantage of the method described here is that the sheet afterdeformation can have vertical walls (within the clearance angle to beable to separate the sheet formed from the die 6 at the end of theprocess), in other words, the part obtained by deforming the sheet canhave faces which extend substantially perpendicularly to the orientationof the sheet before deformation. In the example illustrated in thedrawing, the sheet is initially in a horizontal plane. Afterdeformation, it can then have quasi-vertical faces (before removing thepart from the system).

The forming method and the hybrid forming device proposed here make itpossible to obtain by electro-hydroforming parts with quasi-verticalwalls with a reduced cycle time. The cost price of such parts can thusbe limited.

According to an alternative embodiment, the walls in the tank (thepunch) could for example form a honeycomb type cellular structure.

It is arranged in the embodiment illustrated that the peripheral wall ofthe tank is a part of the punch intended to deform the sheet bystamping. This depends obviously on the sought shape to be given to thesheet. The peripheral wall of the tank is not necessarily part of thepunch. It could for example be arranged in FIG. 3 that the blank-holderis flush with the top edge of the peripheral wall of the tank.

In the device shown, it has been assumed that the tank was stationary.This is a preferred embodiment but it would be possible to have astationary die. A person skilled in the art understands that it is therelative movement between the various constituent elements of the systemwhich is important.

The present disclosure is not limited to the different embodimentsdescribed and illustrated and to the alternative embodiments mentionedbut it also relates to embodiments within the grasp of a person skilledin the art.

The various embodiments described above can be combined to providefurther embodiments. These and other changes can be made to theembodiments in light of the above-detailed description. In general, inthe following claims, the terms used should not be construed to limitthe claims to the specific embodiments disclosed in the specificationand the claims, but should be construed to include all possibleembodiments along with the full scope of equivalents to which suchclaims are entitled. Accordingly, the claims are not limited by thedisclosure.

1. A method for forming a material blank, comprising: placing a materialblank to be deformed between a die and a blank-holder; deforming thematerial blank by stamping using at least one punch in order to obtain apre-stamped material blank; filling a cavity with a liquid, the cavityat least partially defined by the at least one punch, at least one pairof electrodes being located in the cavity and the pre-stamped materialblank being in contact with the liquid in the cavity; and deforming thepre-stamped material blank against the die by generating at least oneelectrical discharge between the at least one pair of electrodes.
 2. Themethod according to claim 1, wherein a relative travel of each of the atleast one punch with respect to the die is limited in such a way thatthe material blank does not come into contact with the die when it ispushed by the at least one punch.
 3. The method according to claim 1,wherein a relative travel of the at least one punch with respect to thedie allows the material blank to come into contact with the die when itis pushed by said at least one punch.
 4. The method according to claim1, wherein the deforming the pre-stamped material blank includespressurizing the liquid in contact with the pre-stamped material blank.5. The method according to claim 1, further comprising creating a vacuumbetween the material blank and the die.
 6. The method according to claim1, further comprising moving the at least one punch away from the dieonly after the generating the at least one electrical discharge.
 7. Ahybrid forming device of a material blank, comprising: a die cooperatingwith a blank-holder, the die being movable relative to the blank-holderbetween an open position in which a material blank can be positionedbetween the die and the blank-holder and can be removed therefrom and aclosed position in which the blank-holder cooperates with the die tohold in a controlled manner an edge of a material blank to be deformed;a tank at least partially defining a cavity capable of being filled witha liquid; and at least two electrodes in the cavity, wherein the tankincludes at least one movable punch relative to an assembly formed bythe blank-holder and the die in the closed position between a farposition in which a free end of the punch is at a distance from the dieand a near position in which the free end of the punch is at a distancefrom the die less than the distance thereof in the far position.
 8. Thehybrid forming device according to claim 7, wherein the assembly formedby the blank-holder and the die in the closed position is movable withrespect to the tank which remains stationary.
 9. The hybrid formingdevice according to claim 7, wherein the tank has a bottom and aperipheral wall, and the free edge of the peripheral wall forms a punch.10. The hybrid forming device according to claim 7, wherein the tank hasa bottom and a peripheral wall, the at least one punch is produced on afree edge of a wall extending through the tank by dividing the latterinto at least two compartments, and the at least two electrodes includesat least one pair of electrodes located in each of the two compartments.11. The hybrid forming device according to claim 7, wherein theblank-holder is attached to vertical, the die is movably mounted intranslation with respect to the blank-holder on a side opposite thestays, the tank includes a bottom and a peripheral wall, and the tank isfixedly mounted whereas the stays are sliding with respect to the tank.